1. Technical Field
The present disclosure relates to a light emitting device and manufacturing method thereof.
2. Description of the Related Art
The light radiation theory of light emitting diode (LED) is to generate light from the energy released by the electron moving between an n-type semiconductor and a p-type semiconductor. Because the light radiation theory of LED is different from the incandescent light which heats the filament, the LED is called a “cold” light source. Moreover, the LED is more sustainable, longevous, light and handy, and less power consumption, therefore it is considered as a new light source for the illumination markets. The LED applies to various applications like the traffic signal, backlight module, street light, and medical instruments, and is gradually replacing the traditional lighting sources.
Generally, the light extraction efficiency depends on the internal quantum efficiency and light extraction efficiency. The internal quantum efficiency can be defined as opto-electrical conversion efficiency in the LED.
The light extraction efficiency refers to the efficiency of the light produced in the light emitting layer extracted from the LED chip. In the meantime, light extraction efficiency is known to depend on the ratio of refraction indexes inside and outside the LED on the light extraction surface, and the surface properties thereof. Normally, the refraction index of the compound semiconductor commonly used as the material of LED is much greater than that of air.